Independent scientists conclude that the shale gas extraction technique is safe but set limits on drilling near water sources
New research confirms the controversial “fracking” technique used to extract shale gas triggered the minor earthquakes in Lancashire in 2011, but concludes that the process is safe to be rolled out in the UK as long as seismic hazards are assessed prior to proceeding.
The DECC-commissioned study reviewed evidence from Cuadrilla Resources, which operates the only shale gas mine in the UK, near Blackpool. The company acknowledged last November that the use of fracking, or hydraulic fracturing, at its Preese Hall mine on the Fylde coast was the likely cause of the minor seismic tremors in April and May last year, and the energy department’s independent assessment agrees.
The review team, which involved experts from Keele University and the British Geological Survey, found that it is safe to resume hydraulic fracturing provided the operators follow recommended procedures, including the introduction of a “traffic light” system that would see fracking halted if it triggers tremors of 0.5 or above on the Richter scale. Tremors measuring 2.3 and 1.5 were recorded in 2011.
Hydraulic fracturing involves the intentional injection of fluids – water, sand and chemicals – at high pressure to create new fissures and release gas deposits that have been locked in shale rock formations for millions of years.
Cuadrilla Resources welcomed the findings of the DECC report. “We are pleased that the experts have come to a clear conclusion that it is safe to allow us to resume hydraulic fracturing, following the procedures outlined in the review,” said the firm’s chief executive Mark Miller, adding that the company had already started to implement a number of the recommendations.
Campaign group Friends of the Earth criticised the review for focusing only on seismic activity. “Earth tremors aren’t the only risks associated with fracking – it’s also been linked to air and water pollution and produces gas that causes climate change. There should be a full scientific assessment of all the impacts,” commented executive director Andy Atkins.
WWF agrees. “The issue of earth tremors is an admittedly worrying distraction. The real concern is the use of fossil fuels,” it said.
The energy and climate change department has given interested parties until 29 May to comment on the review. It will then make a final decision on whether to restart hydraulic fracturing operations at Preese Hall, which have been suspended since the 2011 tremors.
Meanwhile, separate scientific research suggests that fracking should not take place within 600m of aquifers that supply drinking water. According to the study, published in Marine and Petroleum Geology, the probability of fractures extending more than 350m is just 1%, and that fracking to 2km or 3km below the surface was very unlikely to lead to contamination of water supplies, something that campaigners claim in the US, where there are extensive shale gas operations.
Professor Richard Davies, director of the energy institute at Durham University, said: “Based on our observations, we believe that it may be prudent to adopt a minimum vertical separation distance for stimulated fracturing in shale reservoirs. Constraining the maximum vertical extent of hydraulic fractures is important for the safe exploitation of unconventional hydrocarbons such as shale gas and oil.”
He confirmed that with Cuadrilla’s shale gas exploration scheme near Blackpool 3km down, it would not affect water supplies in the area, which are around 300m below the surface.
